diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 9c12fb8..574b9c9 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1,4 +1,4 @@
-*eval.txt*	For Vim version 9.1.  Last change: 2024 Jan 14
+*eval.txt*	For Vim version 9.1.  Last change: 2024 Feb 05
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2005,9 +2005,14 @@
 								*v:colornames*
 v:colornames    A dictionary that maps color names to hex color strings. These
 		color names can be used with the |highlight-guifg|,
-		|highlight-guibg|, and |highlight-guisp| parameters. Updating
-		an entry in v:colornames has no immediate effect on the syntax
-		highlighting. The highlight commands (probably in a
+		|highlight-guibg|, and |highlight-guisp| parameters.
+
+		The key values in the dictionary (the color names) should be
+		lower cased, because Vim looks up a color by its lower case
+		name.
+
+		Updating an entry in v:colornames has no immediate effect on
+		the syntax highlighting. The highlight commands (probably in a
 		colorscheme script) need to be re-evaluated in order to use
 		the updated color values. For example: >
 
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index c4f59ae..1c9f6f2 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2024 Jan 24
+*syntax.txt*	For Vim version 9.1.  Last change: 2024 Feb 05
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -5265,7 +5265,8 @@
 	"cterm=" argument AFTER the "ctermfg=" or "ctermbg=" argument.	Or use
 	a number instead of a color name.
 
-	The case of the color names is ignored.
+	The case of the color names is ignored, however Vim will use lower
+	case color names when reading from the |v:colornames| dictionary.
 	Note that for 16 color ansi style terminals (including xterms), the
 	numbers in the NR-8 column is used.  Here '*' means 'add 8' so that
 	Blue is 12, DarkGray is 8 etc.
@@ -5384,8 +5385,8 @@
 	    :highlight Comment guifg=#11f0c3 guibg=#ff00ff
 <
 	If you are authoring a color scheme and use the same hexadecimal value
-	repeatedly, you can define a name for it in |v:colornames|. For
-	example: >
+	repeatedly, you can define a (lower case) name for it in |v:colornames|.
+	For example: >
 
 	    # provide a default value for this color but allow the user to
 	    # override it.